Supplementary Material for: How Much Liver Tissue Is Required for Sufficient Histological Staging in Patients with Primary Biliary Cholangitis?

Introduction: Histological alterations in primary biliary cholangitis (PBC) are heterogeneously distributed throughout the liver. Thus, the quality of histological staging is probably dependent on the available amount of liver tissue. The goals of this study were to test this hypothesis and to define biopsy conditions for obtaining sufficient tissue. Methods: In this retrospective analysis, we investigated 34 patient cases who fulfilled the criteria of the European Association for the Study of the Liver (EASL) for PBC and underwent a mini-laparoscopic liver biopsy between 2011 and 2018 using 16 or 18G needles. For histological assessment of fibrosis, we used the Ishak score, and the amount of tissue was measured by the number of portal fields. Histological staging was compared with the macroscopic mini-laparoscopic fibrosis score (MLFS), and non-invasive liver stiffness measurements using acoustic radiation force impulse (ARFI) imaging and the FIB-4 score. Results: Biopsy was successful in 33 of 34 patients (97%). Fibrosis assessment by MLFS and ARFI correlated strongly with each other (r = 0.7088, p = 0.000017). However, the correlation of both methods with the histological staging was weaker (MLFS vs. histology: r = 0.4231, p = 0.0142; ARFI vs. histology: r = 0.3564, p = 0.0577). The correlation of ARFI and MLFS with the histological staging was better in the subgroup of biopsies with at least 10 portal fields (= SG_≥10PF) (MLFS vs. histology: r = 0.6369, p = 0.006; ARFI vs. histology: r = 0.7538, p = 0.0012). FIB-4 correlated weakly with the histological staging, which was statistically not significant (all samples: r = 0.2693, p = 0.1296; SG_≥10PF: r = 0.2244, p = 0.3866). The number of portal fields correlated well with the length of the samples (r = 0.6436, p = 0.00012). The probability to attain at least 10 portal fields depended on the needle diameter and number of samples (1 × 16G or 18G [n = 10]: 30.0%; 2 × 18G [n = 15]: 53.3%; 2 × 16G [n = 5]: 100%; p = 0.0414). Conclusion: ARFI and MLFS are probably well suited for the assessment of liver fibrosis in patients with PBC. A minimum of 10 portal fields could improve the histological assessment in PBC and can probably be achieved by obtaining two 16G biopsies.